Description:The Caldera de Las Cañadas is one of the largest calderas in the world. It is elliptical in shape, 16 km across at the widest point, 10 km across at the narrowest and with a perimeter of 45 km. The part that is currently visible is the south wall and runs for some 23 km. The north wall was buried by later eruptions, which have led to the formation of the current Mt. Teide - Pico Viejo stratovolcano, whose lavas have largely filled the original caldera. The Caldera was formed some 170,000 years ago, as the Cañadas volcanic edifice which is believed to have reached a staggering height of 6000 metres altitude, became unstable and collapsed to the north in a massive gravitational landslide. In addition to this, deposits of pumice indicate an explosive eruption at around that time. What is still uncertain however is whether the volcano actually exploded and then collapsed, or first collapsed triggering a catastrophic explosive eruption by decompression, which would have emptied the magma chamber or chambers almost instantly, which then collapsed inwards to form a collapse caldera.